The presently described technology relates generally to the art of polymer films, and more specifically to multilayer elastomeric films containing styrene block copolymer(s) (“SBC”) and a second non-SBC elastomer or plastomer, which exhibit improved film properties in comparison to films comprised of SBC only.
Disposable absorbent articles (e.g., disposable diapers for children or adults) often include elastic features designed to provide enhanced and sustainable comfort and fit to the wearer by conformably fitting to the wearer over time. Examples of such elastic features may include, for example, elastic waist features, elastic leg cuffs, elastic side tabs, or elastic side panels that can provide expansion and contraction benefits to an absorbent article so that the article may conform to the wearer in varying directions. Additionally, such elastic features are often required to be breathable to provide a desired level of comfort to the wearer's skin.
Further, the elastic features of disposable absorbent articles may be made of compound materials comprising elastic films (including breathable films) or elastic scrims, laminated to non-woven fabrics providing desired surface properties and aesthetics of the compound material. The elastic properties of such compound materials are often obtained by activating the elastic properties within the compound, which can be latent before activation, that is the compound material which is non-elastic by itself before the activation becomes elastic after the activation as it were itself elastic.
One of the activation techniques can include mechanical stretching, in particular incremental mechanical stretching. Such mechanical stretching provides permanent elongation of the non-woven substrate(s) comprising the compound material to enable the elastic member(s) of the same compound material (e.g., elastic film or elastic scrim) to stretch under a tension force applied thereto. When the elastic member is allowed to contract, the permanently elongated nonwoven fabric wrinkles or shirrs to contract in at least one dimension along with the elastic member. In doing so, the compound material becomes elastic or an elasticized material.
However, the elasticized materials are often expensive because they cannot only include inexpensive elastic materials, but also require difficult processing and handling of elastic members (i.e., elastic films and scrims). Such processing can include additional and expensive cutting and slip steps or procedures. Thus, because the elasticized features are relatively expensive to produce and include, they typically contribute to a higher cost of various articles produced (i.e., absorbent articles containing such elasticized members).
Another method of allegedly enhancing fit and comfort to an absorbent article is to use elastic strands in its construction. Published United States Application No. 2003/0089454 to Johnson, describes methods for the manufacture of absorbent articles utilizing such elastic strips. Although the reference describes the articles as providing a comfortable and contoured fit to the wearer over time, the construction of such articles with elastic strips often results in a bulky side area of the product.
Moreover, elastic strand products and other elasticized materials are often expensive to produce because of the inclusion of expensive elastomeric materials such as a styrene block copolymer, but also require difficult process operations.
There is market interest based upon aesthetic and economic reasons in replacing the Lycra® or styrene block copolymer elastic strands used today with an elastic film. By incorporating an elastic film rather than Lycra® or styrene block copolymer elastic strands it is believed that the absorbent product would exhibit a flatter-looking side panel. Further, using a single roll of elastic film could eliminate the processing problems inherent with handling many spools of elastic strands. Further, elastic films may not be generally a more cost effective alternative to Lycra® elastic materials.
Thus, there is a need for a low cost multilayer elastomeric film having improved tear strength, and elongation to break, while providing a high elastic recovery, as measured by the permanent set, more typical of an SBC elastomeric film.